Because he was in the right place at the right time.
Because poor matchmaking created poor rankings at WW, with guys like Condit, Rory, and Hendricks going through the toughest schedules to get a title shot, while GSP wasted precious years of his career against people like Hardy and Koscheck.
GSP should have fought Condit and Hendricks much earlier.
Because MMA isn't like other sports where the best face off, even if they "already" faced each other.
Imagine, Federer and Nadal "already played each other", so let's have Dan Hardy face the defending champ instead.